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Preferred Cadence Disparity

The wife and I have had the Rover Tandem for a year now. With a few minor modifications that we've done, we love it in every way except one. It's just the nature of the beast: the two of us do have different preferred cadences and there's no changing that, it seems. I prefer a faster one; she, a slower. When I try to pedal at hers, I feel strained, trying to push harder at the lower foot speed. When she tries to pedal at mine, she says she can hardly keep her feet on the pedals, they're spinning around so fast. I try to set a compromise cadence in the middle, put it's still not real good for either one of us.

Now the overall gear range seems good for us. In gear one we can get up just about any hill we've found; in gear eight, we can run along at as fast a speed as we ever want to go. In between low and high, there's all the differenciation we need. The only issue is setting up the trike so we can both contribute optimum pedal power throughout the gear range, each pedaling at his/her most comfortable cadence. How do I best and least expensively do that?

I have thought the best thing might be to install a different size chainring for the stoker. (I've read about different length pedals for the stoker, but that doesn't seem as reasoned a solution.) The current, factory setup is this:
34 teeth -- front chainring
34 teeth -- outer rear chainring (going back to hub)
30 teeth -- inner rear chainrign (going forward to front crankset)

The source of all our woes may be the two different size chainrings on the rear crankset, forcing her pedals to make more revolutions per unit of distance than do mine. But how can I best remedy this? We have the IPS hub on the rear, so it seems changing out chainrings may not be as simple a task. Can someone help with this? Thanks so much.

Comments

We have the same issue (captain preferring a higher cadence than the stoker), and likewise have IPS added. I think we can help this by swapping the positions of the 30 tooth stoker chainring with the 34 tooth captain chainring. That should increase the cadence of the captain relative to that of the stoker by 25% (cadence change of 20 RPM) compared to the current setting. To do this requires a Park CCP-22 tool to pull the stoker position right crankarm, a Park CNW-2 and a 5mm Allen wrench for the chainring. It's possible a Park BBT-22 bottom bracket tool and torque wrench will also be needed, but presumably you already have all that if you installed the IPS upgrade yourself. Doing only this should not affect the chain length.

One downside is that doing this would also reduce top speed 25%. Our outer stoker position chainring is already at 50 teeth, the largest I could find, so I can't swap in a larger one to compensate. You, on the other hand, likely have a smaller chainring in that position, so can add 25% more teeth to it to maintain your current top speed.

I would love to see a close-up picture or 2 of your setup (at least one on the TT site, would be good, too!)
I have not yet played with or even seen the TT IPS system, so I probably don't yet know enough to give the best possible advise.

But, from reading thunderchunk's post, it sounds like his idea would at least be a big step in the right direction. 34T 74mm BCD-pattern sprockets do exist, though they are not terribly common (because the 74mm pattern is usually paired with a 110mm pattern, which starts at 34t.) I have just one in stock; it's a Campagnolo however, so somewhat pricey at $55. In the past, I also had some cheap ones by Sakae, but ran out of those; someone else might have one.

I believe you said that you have the IPS only on the rear of your tandem (so she can coast when you are still pedaling, if she wants to, but you can't do likewise) so I guess that swapping the positions of your existing front and rear cranks won't work.

I think it is generally a very BAD idea (but very uncommon; this is the only instance I've ever heard of) for any maker to make the stoker pedal at a HIGHER cadence, because the vast majority of husband/wife tandem teams have the exact issue that you and Mr Jim have reported, due to a few common factors: the husband is often more athletically inclined, and just as important, usually has longer feet and longer legs, all which make it much easier to spin at a higher cadence.

The very best solution for this very common issue, in my -and in most current tandem-maker's- opinion is to provide longer crankarms for the captain, and/or shorter ones for the stoker. Most (conventional, 2-wheel) tandems now come with 175mm front and 170 rear, which is better, but often still not quite optimal. Many times a difference of 10 to 15mm works best (or even 50mm or more if the stoker is very short, a child, or has a handicap or restricted range of motion.) Shorter cranks slow down the foot speed at any given RPM, but also (unlike having different-sized timing rings) permit pedaling happily at the same RPMs, which IMO is most conducive to the best possible "tandem experience."

On many of the decent but inexpensive cranks (as those coming on most TT's) with 'fat' arms it is fairly easy to shorten the existing cranks by about 20mm or more, just by careful set-up and use of a drill press to drill and tap a new pedal hole. (Standard 1/2" drill bit, then 9/16" right & left pedal taps as supplied by Park Tool and others. Also, ideally, a facer, to make a perfectly flat seat for the pedal shoulder.)